Elementary Algebra

by
Kaufmann, Jerome; Schwitters, Karen;

Answer

75

Work Step by Step

According to the question, 20 percent of a certain number is 15.
Therefore, we denote the unknown number with $x$ in order to write the following equation:
Step 1: $\frac{20}{100}\times x=15$
Step 2: $20x=100\times15$
Step 3: $20x=1500$
Step 4: $x=\frac{1500}{20}$
Step 5: $x=75$
Therefore, $20$% of $75$ is $15$.